Enable ARCH_EXCEPT macro for non-usermode scenario for RISC-V
Macro will now raise an illegal instruction exception so that mepc will
hold expected value in exception handler, and generated coredump can
reconstruct the failing stack
Coredump tests running on renode (for RISC-V) can now utilize fatal error
path through k_panic
Signed-off-by: Mark Holden <mholden@fb.com>